This invention relates to fuel tanks and more particularly to a fuel tank and fuel flow control device.
As concern for the environment increases, regulations for preventing the escape of volatile hydrocarbon vapors to the atmosphere are being promulgated by governmental agencies. One source of hydrocarbon vapors is the fuel tanks of vehicles using gasoline or other hydrocarbon fuels of high volatility. With current automotive fuel tank designs, fuel vapor can escape during the filling of the tanks and usually even after the tank is filled.
The use of an on-board vapor storage container to remove excess fuel vapor from the fuel tank is one solution to this problem. Some of these devices use a high capacity or high flow rate valve to control the flow of vapor from the fuel tank to a vapor storage canister. From the storage canister, the vapor may be fed into the intake manifold of the engine to be consumed by the engine.
Current on-board vapor recovery systems send essentially all the vapor removed from the fuel tank to the vapor canister. This can produce a high flow rate of fuel vapor to the vapor canister requiring a large vapor canister which increases the cost of the vapor recovery system.
A fuel tank assembly has a fuel tank with a fuel flow control device disposed at least partially in the fuel tank, and which communicates with a fuel filler pipe through which fuel is added to the fuel tank. In one embodiment, the fuel flow control device includes a fill tube that controls the manner in which fuel enters the fuel tank, preferably to reduce generation of fuel vapor when fuel is added to the fuel tank. In one presently preferred embodiment, the fill tube is constructed and arranged so that fuel exits therefrom generally at the surface level of fuel in the fuel tank. In the embodiment disclosed herein, this is accomplished by providing the fill tube as a flexible tube and including a float adjacent to an outlet end of the fill tube, so that the outlet end of the tube is responsive to the level of fuel in the fuel tank for at least some levels of fuel in the fuel tank.
In another presently preferred embodiment, the fuel flow control device includes a diffuser through which fuel flows. Preferably, the flow area of the diffuser increases as it extends downstream, decreasing flow velocity and increasing pressure to reduce fuel vapor generation and encourage condensation of fuel vapor. Desirably, the diffuser can also function as a fuel filter. The diffuser can be used with a fill tube, and may be maintained generally in the area of the surface level of fuel in the fuel tank, along with an outlet end of a fill tube, if used with a fill tube. With the diffuser on the bottom of the tank the hydrostatic pressure can increase the condensation of vapor.
Some objects, features and advantages of the presently preferred embodiments of the invention include providing a fuel tank assembly and fuel flow control device that reduce fuel vapor generation during refueling of a fuel tank, permit use of a smaller vapor canister, permit use of a lower cost vapor canister, reduce hydrocarbon emissions, reduce premature shut-off of a refueling nozzle, reduce spit back during refueling, can provide an additional or alternative source of fuel filtration, and are of relatively simple design and economical manufacture and assembly.
The above noted objects, features and advantages are not intended to be complete, but rather, are merely illustrative of certain aspects of some presently preferred embodiments of the invention. Accordingly, in practicing the invention none, some, all and/or other objects and advantages may be achieved.